Light Curing Device

ABSTRACT

The invention relates to a light curing device for dental purposes having a plurality of semiconductor light sources, each light source includes a light-emitting chip, wherein said chips are mounted on a common and chip-cooling substrate. Each chip is surrounded by an individual reflector body connected to the substrate and/or the chip associated therewith, and the reflector bodies of at least two chips are arranged next to one another but are not connected with one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/942,293, filed Nov. 9, 2010, which claims the benefit of EuropeanPatent Application Ser. No. 09178725.9, filed Dec. 10, 2009, all ofwhich are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The invention relates to a light curing device having semi-conductorlight sources, and more particularly to a light curing device for use indental applications.

In prior art light curing devices such as that disclosed in U.S. Pat.No. 6,695,614, which is hereby incorporated by reference, recesses areformed in a common copper substrate, and the recesses receive chips thatserve for the emission of light. This solution has the advantage thatall chips substantially have the same temperature due to the solidcopper substrate, and good heat dissipation is ensured. The lightemission, however, in this solution requires improvement due to thesmall reflectors.

In order to improve the light emission it has been proposed to providecollecting lenses above individual reflectors of this kind.Nevertheless, the light efficiency is not particularly high. This alsoapplies to solutions known from U.S. Pat. Nos. 7,001,057 and 6,767,109,which are hereby incorporated by reference. Here, the reflectors, atleast partially, are applied as raised bodies that surround the LEDchips in a tight manner.

Moreover, it has already been proposed to use LED lamps with parabolicreflectors, in which case reference is made to, for example, DE 10 2004007 812 A1, which is hereby incorporated by reference.

Further, it has already been proposed in-house to employ enlargedreflectors that are commonly constructed from one solid body, whereinthe individual reflectors intersect one another. Surprisingly, however,the light emission is comparatively unsatisfactory with such a solutionso that this solution has not been pursued further.

In particular, with light curing devices for dental purposes, however,light emission must be sufficient and within the specification. Aninsufficient light emission may lead to the result that the dentalmaterial to be polymerized is not fully cured resulting not only inremaining free radicals but in particular in the overall restoration notbeing sufficient and thus causing regular customer complaints.

SUMMARY OF THE INVENTION

It is therefore an object of an embodiment of the invention to provide alight curing device for dental purposes having a plurality ofsemiconductor light sources that each comprise a light-emitting chip,wherein said chips are mounted on a common substrate that, in particulardissipates heat. The several chips may be driven separately or together,wherein the light emission is improved in comparison to the multiplearrangements or arrays of LED chips which have been known so far.

It is a further object of an embodiment that each chip is surrounded byan individual reflector body connected to the substrate and/or the chipassociated therewith, and at least two reflector bodies are arrangednext to one another but are not connected with one another.

According to an embodiment of the invention, the light emission of theinventive light curing device is improved in particular at highperformance. According to an embodiment of the invention, high-qualityoptics shared by all chips may be used, and the light emission thereofsurprisingly is close to the theoretical maximum.

According to an embodiment of the invention, the thermal decoupling ofthe individual reflector bodies may result in the fact that they do notdeviate from their predetermined optical axis. This allows the use ofhighly reflective metal or plastic bodies as reflector bodies, thethermal expansion coefficient of which is comparatively large butnevertheless enables an axis constancy of the reflector. Apparently, thereflector bodies which have an inner parabolic shape, then deformsymmetrically without the LED chips departing from the focus, and noaxis error arises as it is the case with already known solutions inwhich the reflectors quasi or partially move outwardly due to thethermal stress, i.e., the expansion.

An especially favorable inventive embodiment thus provides that theadjacent reflector bodies are separated by a gap from one another, saidgap preferably extending across the entire separating gap or slitbetween the adjacent reflector bodies in equal width. It is to beunderstood that a reflector body may be of metal construction and inthis case at the same time provides for a certain cooling function oreffect for the heat dissipated, or it may be made of plastic with acorresponding internal metallization.

The gap preferably extends in a straight manner, at least as far asadjacent reflectors are concerned, and in a tangential manner withrespect to each associated reflector cone of the reflector body.

In this connection, reflector cone refers to any suitable formed bodywhich has been optimized for the light emission, even if the reflectorcone is substantially merely cone-shaped, or parabolic, for example.

In order to improve the heat dissipation with an alternating operationof the LED chips that may also emit different wavelengths, it ispossible to connect the reflector bodies if they are of metallicconstruction, via the substrate mechanically and also thermally.

In this case a large contact surface for the reflector body is preferredthat preferably may comprise a significant wall thickness of, forexample, ¼ of the diameter of the light emitting surface of eachreflector body. It is to be understood that the wall thickness of theindividual reflectors may be adapted to the requirements in a wide rangeof sizes. For example, a wall thickness of ⅓ or ⅕ or ⅙ of the lightemission surface of the individual reflector body may be selected orfrom a range of from about ⅓ to about ⅙ of the light emission surface ofthe individual reflector body.

It is to be understood that the individual reflector bodies, if needed,may be provided with heat-dissipating means at the exposed outercircumference thereof, for example with cooling fins, or by means of acontact with a large-area heat-dissipating body.

According to an embodiment of the invention it is particularly favorableif the individual reflector bodies, if necessary apart from the areathat immediately surrounds the LED chips, are thermally isolated anddecoupled from one another such that even in case of a correspondingexpansion the individual reflectors do not touch one another.

According to an embodiment of the invention it is particularly favorableif the reflector bodies at least in the cold state are separated fromone another through a gap therebetween.

According to an embodiment of the invention it is particularly favorableif each reflector body in particular is of metallic construction and inparticular comprises a substantially uniform wall thickness.

According to an embodiment of the invention it is particularly favorableif each reflector body comprises a reflector cone that substantially hasan obtuse parabolic inner shape, and that the openings of the reflectorbodies on the light exit side are located in one plane and that the LEDchips are each arranged in the focus of the parabolic or conic section.

According to an embodiment of the invention it is particularly favorableif each reflector body is connected with the substrate in apositive-locking manner, and in particular comprises at least oneprotrusion at an end region opposite to the light exit direction, saidprotrusion engaging into a recess or opening of the substrate.

According to an embodiment of the invention it is particularly favorableif at least one protrusion that faces outwardly from the outer surfaceof the reflector is provided on each individual reflector, and that inparticular protrusions or fins or projections are provided that protrudefrom the reflector bodies and increase the cooling surface of thereflector body.

According to an embodiment of the invention it is particularly favorableif the individual reflectors are thermally connected to one anotherthrough a gap-free and tight fit or rest on the substrate via thesubstrate.

According to an embodiment of the invention it is particularly favorableif a collecting lens or a transparent cover disk covering the reflectorbody is arranged on the light exit side opening region of at least onereflector body.

According to an embodiment of the invention it is particularly favorableif the semiconductor light sources are arranged at the front end of ahand-held light curing device.

According to an embodiment of the invention it is particularly favorableif a light-conducting element, in particular in the form of alight-conducting rod, is arranged in the light exit direction after thesemiconductor light sources.

According to an embodiment of the invention it is particularly favorableif the semiconductor light sources emit light at a wavelength of 350 to480 nm and that in particular at least two adjacent light sources emitlight of different wavelength.

According to an embodiment of the invention it is particularly favorableif adjacent reflector bodies do not intersect one another and if thewall thickness of the reflector bodies in the direction towards theadjacent reflector body at the top end surfaces thereof is reduced to atleast half the wall thickness, in particular to less than 1/10.

According to an embodiment of the invention it is particularly favorableif each reflector body comprises a uniform wall thickness across atleast half of its circumference, said wall thickness in particularamounting to at least ⅛, preferably approximately ¼ of the light exitdiameter of the reflector body.

According to an embodiment of the invention it is particularly favorableif at least two and at most five, in particular, at most four reflectorbodies are arranged adjacent to one another on a common substrate,preferably, three reflector bodies.

According to an embodiment of the invention it is particularly favorableif the gap between the reflector bodies in the cold state has a widththat is calculated so that the reflector body upon transition from thecold to the hot state, protrudes into the gap at most, half the width ofthe gap.

According to an embodiment of the invention it is particularly favorableif the light curing device at least comprises one sensor that isarranged on the substrate or that is connected with the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, details and features become apparent from thefollowing description of embodiments of the invention with reference tothe drawings, in which:

FIG. 1 illustrates a schematic perspective view of the light source ofan embodiment of a light curing device for dental purposes according tothe invention.

FIG. 2 illustrates a further perspective view of the embodiment of FIG.1.

FIG. 3 illustrates a view of the embodiment of FIG. 1, in a viewdirected obliquely from below.

DETAILED DESCRIPTION

FIG. 1 illustrates a light curing device 10 according to an embodimentof the invention that comprises a light source 12 having a plurality ofsemiconductor light sources. These include three light-emitting chips14, 16 and 18 that are mounted on a common and chip-cooling substrate20. It is preferable that the three light emitting chips 14, 16 and 18are all identical in their dimensions and shape and are arranged in acloverleaf-like shape.

Each chip is surrounded by a reflector body, i.e. chip 14 is surroundedby reflector body 22, chip 16 is surrounded by reflector body 24 andchip 18 is surrounded by reflector body 26. The individual reflectorbodies 22 to 26 are each supported by the substrate 20 and mountedthereon.

At least above the chips 14, 16 and 18, a gap is provided between theindividual reflector bodies 22 to 26, namely gap 30 between thereflector bodies 22 and 26, gap 32 between the reflector bodies 22 and24 and gap 34 between the reflector bodies 24 and 26. These gapscomprise an inventive width that is selected such that even in case ofan enlargement of the individual reflector bodies 22 to 26, therespective gaps 30 to 34 are not bridged, so that the reflector bodies22 to 26 are always mechanically separated without abutting on oneanother or engaging with one another.

It is to be understood that the mounting of the individual reflectorbodies 22 to 26 on the substrate 20 is selected to be sufficientlydimensionally stable and firm such that an abutment or attachmentbridging the gap does not arise even in case of vibrations.

If one of the LED chips 14 to 16, for example, has an edge length of 5mm, each gap 30 to 34 in the cold state may have a size of 0.5 mm, forexample, wherein it is to be understood that the required gap width maybe ascertained either by calculation or by experiments.

According to an embodiment of the invention it is provided that thereflector bodies 22 to 26 are manufactured to be quite thick. Forexample, the wall thickness of the reflector bodies may amount toapproximately 4 mm, and it is possible to adapt to the requirements inlarge areas.

According to an embodiment of the invention the wall thickness of thereflector bodies each is notedly reduced relative to one another inorder to provide the gap 30 to 34 in the adjacent areas of the reflectorbodies 22 to 26, in particular in the top area, that is to say, in thearea of the light exit surface 40 of the individual reflector bodies 22to 26. At this location for example, the wall thickness may be reducedto gap width or even to half the gap width, wherein according to theinvention it is preferred that the individual reflectors do notintersect one another.

Accordingly, each reflector body 22 to 26 preferably comprises aparabola frustrum-shaped or paraboloidal-shaped inner surface 42,wherein, in an embodiment, the LED chips 14 to 18 are each arranged inthe focus of the parabola-frustrum shaped inner surface 42. As can beseen from FIG. 1, the light exit openings of each of the individualreflector bodies are arranged very close to each other, comprise asubstantially circular shape and said openings do not intersect

From FIG. 2 it becomes apparent that the gap 34 between the adjacentreflector bodies 24 to 26 extends to the substrate 20, thus iscompletely drawn through to the bottom. The third gap is both uniformwith respect to width and height such that each LED chip 14 to 18 eachremains at its given position irrespective of the movement of thereflector bodies 22, 24 and 26.

Even when the substrate 20 here is illustrated to be a comparativelythin and little compact, it is to be understood that in practice asubstantial thermal stress is also present there. Accordingly, thethermal dissipation resistance of the substrate 20 in practice is lowwhich is ensured by providing respective coolants (not illustrated).

According to an embodiment of the invention, due to specific optics thatare attached in front of the reflector bodies 22 to 26, the axialposition of the LED chips shall not be changed which means that not onlya “deflection” of the individual reflector bodies must be prevented.

Preferably, the light emitting surfaces 40 or the openings on the lightexit side of the reflector bodies are arranged in one plane whichbecomes apparent from FIG. 2. This plane may form a bearing surface 50either for individual collecting lenses or for a common collecting lensfor the light source 12 or for sophisticated optics that concentratesand focuses the light emission in a way that is particularly favorablefor the given application purpose, i.e., the light curing process ofdental materials.

It is to be understood that a transparent cover disk may be providedinstead of the collecting lens or in addition thereto that also servesas a thermal separation between the collecting lens and the reflectorsand in this way prevents the deformation of the optics due to a heatingof the reflector bodies.

According to an embodiment of the invention, the light source 12 may bearranged both at the front end of a hand-held light curing device and inthe base thereof, whereby in the second case it is preferred that alight-conducting rod extends from the light source 12.

It is preferred that protrusions or projections or fins 52, 54 and 56are provided for the mechanical attachment of the light source 12,wherein the protrusions may be formed at the exterior/front of eachindividual reflector 22 to 26 and face to the outside and preferably notexceed the above-mentioned plane. At this position, each reflector body22 to 26 is comparatively cold, as the heat is primarily introduced atthe base of each reflector body 22 to 26. The absorption at thisposition in this respect is also possible without constructively exigentthermal damping measures.

FIG. 3 shows that the reflector bodies 22 to 26 each comprisedownward-facing protrusions 60, 62, 64, 66, 68 and 70, that is, eachreflector body 22, 24 and 26, comprises two protrusions that passthrough the substrate 20 and which provide for a form-fitting anchorage.In this connection it is particularly favorable if the connecting linebetween two protrusions of a reflector body, that is, for example, ofthe protrusions 60 and 70 of the reflector body 26, is below therespective LED chips of the reflector such that a symmetrical guidanceis ensured in this respect in case of a possible thermal expansion ofthe substrate 20.

All numbers expressing quantities or parameters used in thespecification are to be understood as additionally being modified in allinstances by the term “about”. Notwithstanding that the numerical rangesand parameters set forth, the broad scope of the subject matterpresented herein are approximations, the numerical values set forth areindicated as precisely as possible. For example, any numerical value mayinherently contains certain errors, evidenced by the standard deviationassociated with their respective measurement techniques, or round-offerrors and inaccuracies.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without department from thespirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A light curing device for dental purposes comprising: a plurality of semiconductor light sources; wherein each light source comprises a light-emitting chip; wherein the light-emitting chips are mounted on a common substrate that dissipates heat; wherein each light-emitting chip is surrounded by an individual reflector body connected to the substrate and/or the light-emitting chip associated therewith; at least two reflector bodies are arranged next to one another but are not connected with one another; wherein a collecting lens or a transparent cover disk is arranged on a light exit side opening region of at least one reflector body; wherein the light curing device is a hand-held light curing device and wherein the semiconductor light sources are arranged at a front end of a hand-held light curing device.
 2. The light curing device as claimed in claim 1, wherein the reflector bodies at least in the cold state are separated from one another by a gap.
 3. The light curing device as claimed in claim 1, wherein each reflector body is of metallic construction and comprises a substantially uniform wall thickness.
 4. The light curing device as claimed in claim 1, wherein each reflector body comprises a reflector cone that substantially has an obtuse parabolic inner shape, and wherein the openings of the reflector bodies on the light-emitting side are located in one plane.
 5. The light curing device as claimed in claim 1, wherein each reflector body is connected with the substrate in a positive-locking manner, and comprises at least one protrusion at an end region opposite to the light exit direction, said protrusion engaging into a recess or opening of the substrate.
 6. The light curing device as claimed in claim 1, wherein projections are provided that protrude from the outer surface of the reflector bodies and increase the cooling surface of the reflector body.
 7. The light curing device as claimed in claim 1, wherein the individual reflectors are thermally connected to one another through a gap-free and tight fit or rest on the substrate via the substrate.
 8. The light curing device as claimed in claim 1, wherein a light-conducting element is arranged in the light exit direction after the semiconductor light sources, said light-conducting element is in the form of a light-conducting rod.
 9. The light curing device as claimed in claim 1, wherein the semiconductor light sources emit light at a wavelength of 350 to 480 nm and wherein at least two adjacent light sources emit light of different wavelength.
 10. The light curing device as claimed in claim 1, wherein two to five reflector bodies are arranged adjacent to one another on a common substrate (20).
 11. The light curing device as claimed in claim 1, wherein the light curing device comprises at least one sensor arranged on the substrate or connected with the substrate.
 12. The light curing device as claimed in claim 2, wherein the individual reflector bodies are mounted on the common substrate, wherein the gap formed between each adjacent reflector body is not bridged upon expansion of the reflector bodies.
 13. The light curing device as claimed in claim 12, wherein each gap between each adjacent reflector body extends from the top to the bottom of the reflector body.
 14. The light curing device as claimed in claim 4, wherein each light-emitting chip is surrounded by an associated individual reflector body, wherein the light-emitting chips are each arranged in the focus of the obtuse parabolic shaped inner surface of the respective individual reflector body.
 15. The light curing device as claimed in claim 4, wherein at least three reflector bodies are mounted on a common substrate, each of the reflector bodies being identical in dimension and shape, wherein the reflector bodies are arranged in a cloverleaf-shaped manner.
 16. The light curing device as claimed in claim 1, wherein the individual reflector bodies are mounted on the common substrate, wherein the openings on the light emitting side of each individual reflector body are located in one plane, wherein said openings of each of the individual reflector bodies comprise a substantially circular shape, and wherein said openings do not intersect.
 17. The light curing device as claimed in claim 1, wherein the individual reflector bodies are mounted on the common substrate, wherein each reflector body comprises a substantially uniform wall thickness except in the area of the reflector body adjacent another reflector body in order to provide gaps between the individual reflectors bodies. 